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Topic: 8MB Ramdisk (external RAM) for Arduino.. (Read 36496 times) previous topic - next topic


Jan 05, 2015, 06:33 pm Last Edit: Jan 05, 2015, 06:45 pm by EvIl_DeViL
sorry for necroposting but I was hoping to buy one of these but they seems out of production... so what do you think about this + this?

basically is a retail sdr ram TSOP-54 chip mounted on a DIP-54 adapter for breadboard. the speed it's not a problem because according to the datasheet which on page 20 states
21. For operating frequencies ≤ 45 MHz, tCKS = 3.0ns
seems we can get quite slow...
refresh is a problem neither because this module also feature autorefresh. They are also 3.3V ±0.3V!!!

mounting can be optionally made by the adapter retailer so even n00bs like me could afford prototyping. cost seems reasonable too... If this solution is working we can access infinite RAM on our DUE module, useful for example for big image manipulation (e.g. 10MP camera sensor)! in this case I'm talking about 512MB (64Mb) in 64MX8 configuration.
To quench the thirst of pin of this beast we could use shift registers or multiplexers for data and address

I've seen ram modules even in commercial cheap-o stuff http://youtu.be/1EuBRmfJLSk @19:37 in the upper part. and here the same module mounted over a ram bank http://old-pc-museum.narod.ru/olderfiles/1/64Mb_eliteMt_m12l64164a-8t_big.jpg.


The sdrams are quite cheap, but not easy to interface. If the DUE supports an sdram interface then it would be doable, otherwise, you have to write a bitbanging driver for it. We did it once with pic32mx and the result was moderate.

The 8MB ramdisk uses an PSRAM - it is an sdram with pure sram interface. Therefore you work with static sram design while utilising large sdram volume.

The static srams are expensive - 8MB of static sram would cost you a lot of money.

Also, when talking micro-controllers, you want to save the i/o pins for something else. An 8MB sram needs about 34 pins in an 8bit data width configuration.

So, you have to balance all possible requirements..

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